This invention relates generally to lock assemblies used to secure doors. More particularly, the present invention relates to a convertible door lock latch mechanism developed for use with a hybrid lock architecture designed to incorporate the functionality of a cylindrical lock architecture with the ease of installation of a tubular lock architecture.
There are currently two main types of lock architectures in widespread use today. These lock architectures are typically known as the cylindrical lock and the tubular lock designs. Each of these designs has advantages and disadvantages in comparison to the other.
While there are variations, traditionally, a cylindrical lock consists of a chassis, an inside mounting plate, an outside mounting plate and rose, an inside rose, a fixed backset latch, an inside and outside knob/lever, and mounting screws. The fundamental workings of the cylindrical lock provide the conversion of rotational motion of the knob/lever to linear motionxe2x80x94within the chassis housingxe2x80x94to retract the latch. The typical cylindrical lock architecture uses a drawbar occupying the axis of the latch bore. These type drawbars reduce the stroke or extension of the bolt due to clearance issues with other lock components. The cylindrical lock architecture typically is more expensive to manufacture, but allows more functional variations than a tubular lock and generally provides better security. The chassis has a fixed spindle-end to spindle-end length which easily accommodates a push-button locking mechanism, however this also results in a varying distance from the end of the knob/lever to the surface of the door when used with different door thicknesses. Installation of a cylindrical lock is generally more complicated than that of a tubular lock. During installation of the cylindrical lock, the inside knob/lever, rose, and mounting plate need to be removed. The chassis needs to be centered in the door by adjusting the outside rose. Additionally, the design constraints inherent in the cylindrical architecture make it impossible to have a dual backset latch which does not require some type of adjustment. Where available, these adjustable backsets used in cylindrical locks are failure-prone and inferior to fixed backset latches.
A tubular lock architecture traditionally consists of an inside chassis complete with a rose and a knob/lever attached, an outside chassis also complete with a rose and a knob/lever attached, a latch, and mounting screws. This simple design allows for easy and quick installation of the tubular lock design with virtually no adjustment required. Due to its simplicity, the tubular architecture also provides a cost advantage over the cylindrical lock. The tubular lock design also provides a fixed distance from the surface of the door to the end of the lever even when used with different door thicknesses. The tubular lock architecture converts rotational motion of the knob/lever to linear motion within the latch in order to retract the latch. Accordingly, a drawbar occupies the axis of the latch bore. However, due to the edge bore of a door preparation, the amount of latch retraction is restricted. Other problems are found in that design constraints make it impossible to design a consistently functioning push button lock because of the chassis datum on the surface of the door. Since the door thickness variation is considerably greater than the push button linear travel, no direct means are available to provide a secure consistent locking action. The tubular lock architecture is also generally less secure than a cylindrical lock architecture.
Accordingly, there remains a need in the art for a lock architecture which combines the advantages of both the tubular lock architecture and the cylindrical lock architecture along with other advantages, while minimizing or removing the limitations existing in each of the prior art designs. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.
It is therefore an object of the present invention to provide a new convertible door lock latch mechanism designed in a first embodiment as a new dead latch assembly and easily converted to a second embodiment as a spring latch assembly. These and other improvements are provided by various embodiments of the present invention, the first of which is a dead latch assembly for a door comprising a drawbar, slidably attached to a bolt by a dead latch stop, and a dead latch plunger, all housed in a bolt housing. The bolt and the dead latch are biased in an extended position at least partly protruding from the bolt housing. The dead latch with assembly is easily converted to a spring latch assembly by removing the dead latch plunger, removing the dead latch plunger spring, and removing the dead latch stop. A pull component is then attached to the bolt.
It is a further object of the present invention to provide a restore component which causes retraction of a drawbar when a bolt of the door lock latch mechanism is depressed. These and other improvements are provided by a door latch assembly which utilizes a restore component positioned between a drawbar and a bolt of the latch assembly.
It is still another object of the present invention to incorporate the new convertible door lock latch mechanism with a new hybrid lock architecture designed to incorporate the functionality of a cylindrical lock architecture with the ease of installation of a tubular lock architecture. These and other improvements are provided by a lock assembly for a door comprising a chassis assembly mounted in a bore of the door. A door latch assembly is operably connected to the chassis assembly for retraction and extension of the bolt. A handle is mounted on a spindle on either side of the chassis assembly. Rotational motion imparted on one of the handles is converted to linear motion within the chassis assembly in order to retract a bolt of the door latch assembly. The door latch assembly comprises a dead latch stop connected to the bolt of the door latch assembly.